Primer



Nov. 6, 1962 c. o. WILLIAMS ETAL 3,

PRIMER Original Filed March 15, 1956 FIG. 2

INVENTORS. Omrus 0 M; x mms I 7mm? )t/fi/a xecms 4 P435271. 5/117 5/ 59 45 40 44 3a WHMRL %Y United States Patent Ofilice 3,062,146 PRllViER Charles 0. Williams, Alton, Victor W. Drexelius, Ed-

wardsville, and Robert D. Smith, Alton, 111., assignors to Olin Mathieson Chemical Corporation, East Alton, Ill., a corporation of Virginia Original application Mar. 15, 1956, Ser. No. 572,177, now Patent No. 2,974,592, dated Mar. 14, 1961. Divided and this application Sept. 29, 1960, Ser. No. 64,673

3 Claims. (Cl. 10246) This invention relates generally to cartridges containing a smokeless powder fuel and more particularly to a cartridge of this type adapted for the operation of ejection mechanisms on airplanes or for use as a power unit in other apparatus. This application is a division of copending patent application Serial No. 572,177, filed March 15, 1956, now Patent No. 2,974,592.

It is often desirable and sometimes necessary to eject certain articles such as fuel tanks, ordnance stores and the like from an airplane while in flight. Such expulsion is ordinarily achieved by actuating the releasing mechanism by means of fluid pressure. One of the more successful means of developing the fluid pressure is to fire a suitable cartridge containing smokeless powder in a confined chamber and use the fluid pressure developed to activate the piston or other mechanism.

It is, therefore, an object of this invention to provide an improved smokeless powder cartridge adapted for use as a power unit to perform mechanical work. A further object of the invention is to provide a novel chamber and cartridge combination which insures ejection of surplus articles from the plane while in flight. Another object of the invention is to provide a cartridge adapted to be ignited and to more reliably develop fluid pressure capable of activating ejection mechanisms in an airplane at various altitudes up to 50,000 feet or more and at temperatures varying from as low as minus 65 F. or lower and as high as 165 F. or more. A more specific object of the invention is to provide a cartridge for use as a power source that is moistureproof and is adapted to be fired without substantial gas leakage from the cartridge into the mechanism used to initiate the explosive fuels in the cartridge.

Other objects will become apparent from the following description with reference to the accompanying drawing in which FIGURE 1 is a longitudinal sectional view of an embodiment of the cartridge provided by this invention;

FIGURE 2 is a sectional view of an embodiment of the primer of the cartridge shown in FIGURE 1;

FIGURE 3 is a sectional view of a chamber having cartridges therein adapted to be associated with mechanism adapted to expel articles from a moving airplane;

FIGURE 4 is a sectional view of another embodiment of a primer; and

FIGURE 5 is a fragmentary section of the cartridge case head.

In accordance with this invention, the foregoing objects and others are achieved generally speaking by providing a cartridge containing a fuel, a smaller charge of a kindling composition separated from the fuel, a moisture proof end closure, and a primer to ignite the kindling composition so constructed that, upon firing, the fluid pressure from the cartridge is exerted only through a rupturable sidewall and upon opening of the end closure. Ordinarily, cartridges are designed so that the fluid pressure escapes through the end closure or about the primer, or both. More specifically, it has been found that a cartridge embodying the combination of an electrically ignitable primer with an easily ignitable fuel that s adapted to ignite a slower burning powder not ignltable 3,062,146 Patented Nov. 6, 1962 by the primer and having an end closure which is moisture proof at high altitudes of up to 50,000 feet or more is particularly advantageous for ejecting stores, fuel tanks and the like from a moving airplane. The closure is in the form of a flanged wad set upon an annular ring or indentation formed adjacent the end of the case. The crimp must contain a suitable sealer against moisture between the shoulder of the annular ring and the base of the Wad, and must also have a sealer along the juncture of the folded-over portion of the cartridge case with the flanged wad in order to prevent moisture from entering the cartridge and deleteriously effecting the fuel. The primer must be provided with a means for heating a resistance wire embedded in a suitable priming mix without short circuiting of the current to the wall of the cartridge case and must be sealed in the pocket of the cartridge case head to prevent gas leakage as the fuel is burned. The priming composition must be ignitable by a resistance wire heated with an electric current at the voltage available on airplanes; usually not more than 25 volts.

The primer must be adapted to be ignited electrically and must fit in the cartridge case in such a way that gases developed as the fuel in the cartridge burns cannot escape between the primer and the wall of the pocket. In order to achieve a seal between the primer and cartridge case, a coating of a suitable resinous material is applied either to the wall of the primer or to the wall of the cartridge case pocket, or both, before the primer is inserted into the pocket. The primer is seated in the pocket while the resinous material is still Wet with solvent and the solvent is then removed by air drying at room temperature or by heating the assembled cartridge to evaporate the solvent. The temperature, of course, to which the cartridge can be heated safely is dependent upon the heat stability of the priming explosives so care must be taken not to heat to a temperature where the explosives will be adversely affected or will be initiated. Any suitable resin such as polyvinyl chloride, polyvinyl acetate, ethyl cellulose, or the like, in a suitable liquid carrier may be used to seal the joint between the primer and primer pocket but it is preferred to use an epichlorhydronbisphenol A polymer because it has been found particularly advantageous as a sealant against gas leakage about the primer when the cartridge is fired. The resin is dispersed in a suitable liquid, and is preferably dissolved in a solvent such as acetone, ethyl acetate or the like to prepare it for application to the primer or primer pocket. As will become more apparent hereinafter, the primer may be either cupshaped or rivet-shaped.

By easily ignitable fuel as used herein and in the appended claims is meant a kindling composition or booster ignitable by a priming composition similar to those used in conventional ammunition cartridges and adaped to ignite the larger main fuel. By main fuel as used herein is meant the larger fuel charge which develops the main portion of the fluid pressure when the cartridge is fired. Referring now to the accompanying drawing for a description of embodiments thereof, the embodiment of FIGURE 1 has an aluminum cartridge case 1 having a thickened head portion 2 and a primer assembly 3 charged with an easily ignitable fuel 8. Immediately above fuel charge 8 is a combustible flanged cup-shaped wad 6 havings its flange engaging the wall of cartridge case 1. A main fuel charge 7 which is not ignitable by primer 3 substantially fills that portion of the cartridge case above wad 6. An annular inwardly extending ring 26 is formed in the wallet cartridge case 1 a short distance from the mouth thereof and a combustible flanged plastic wad 5 is inserted in the mouth of the cartridge case and pressed against the shoulder of ring 26. The Wad 5 is inserted with its flange extending outwardly and its base resting against ring 26. Top wad 5 is coated with cellulose acetate butyrate containing about 0.5 percent paraflin wax or other suitable wax to improve its moisture resistance. The cellulose acetate butyrate coating is applied to the wad as a lacquer prepared by dissolving it and the wax in a solvent such as ethyl acetate, acetone, methyl ethyl ketone, toluene, or the like. Any other suitable moisture proofing lacquer may be utilized instead of the cellulose butyrate lacquer, if desired. Examples of other suitable moisture proof coatings for top wad 5 include polyvinyl chloride, polyvinyl acetate, nitrocellulose base lacquers, either containing small amounts of Wax or Without depending upon the moisture resistant properties of the particular resin utilized. A layer of moisture proofing sealer 30 is placed between the shoulder of the ring or annular indentation 26 and the base of Wad 5. That portion of the cartridge case extending above Wad 5 is turned over and encloses the flange of the wad and presses the base of the wad against ring 26. A fillet of sealer 31 lies between the edge of the turned over portion and the external surface of the wad 5 to form a moisture proof juncture between the end of the cartridge case and the wad.

Referring to FIGURE 2, an embodiment of the primer provided by this invention is composed of a brass, substantially cup-shaped cylinder 11 having an open end and an end partially closed by a flange integral with and perpendicular to the sidewalls. A button 27 having a cylindrical protuberance 28 adapted to protrude through the opening in the partially closed end of cup 11 and a smaller cylindrical shaped protuberance 16 at the other end is separated from the inner wall of cup 11 by means of an annular ring or gasket of dielectric material 14-. A Washer 12 made from a suitable dielectric material rests on the upper surface of button 27 in FIGURE 2 and about the sides of protuberance 16. Protuberance 16 extends though the dielectric material and rests against a resistance wire 17. It is preferred to solder Wire 17 to protuberance 16. The resistance Wire 17 is embedded in a primer composition adapted to ignite the propellent charge 8. The priming composition 10 is housed in a metallic cylinder 29 having a flange about one end thereof partially closing that end. The flanged portion rests on the dielectric washer 12. This cylinder 29 fits snugly in cup 11 and has its open end resting on the bottom of the primer cup thus supporting button 27.

A fixture 18 adapted to cooperate with the cartridge provided by this invention is illustrated in FIGURE 3. Actually two chambers are utilized. Each chamber designated 27 and 28 in the drawing is threaded near the open end thereof and having sleeves 19 and 29 threadably secured therein. Cartridge case 1 is contained in these sleeves with the crimped end located adjacent the closed end of the sleeves and with the head of the cartridge lying against a suitable electrical means for initiating the primer 3 of the cartridge lying thereagainst. The two chambers are connected by port 24 and an annular channel communicates with the port and extends around the chamber. Sleeves 19 and 29 are provided with a plurality of openings which communicate with this channel. A channel 25 extends from chamber 28 to the passageway of tubular fitting 22. The latter tube is adapted to be threadably or otherwise attached to the mechanism to be actuated by the fluid pressure developed when the cartridges are ignited.

Fixture 18 of FIGURE 3 is provided with two chambers to insure ignition of the cartridges when desired. Two cartridges are utilized in preference to one cartridge twice as large because in this way it is only necessary that at least one cartridge be ignited by the primer. In other words, even though one primer fails to ignite because of a failure in an electrical connection or for some other reason the cartridge will be ignited because cartridge case 1 is adapted to burst adjacent the plurality of holes in the sleeves 19 and 29 and hot gases from one cartridge will pass through port 24 to the other cartridge. These gases will burst or burn a hole in the wall of the other cartridge or enter through wad 5 and thus ignite the fuel charge even though the primer in that cartridge has not been ignited. Such an assembly of two cartridges thus provides a safety factor not available if only one cartridge is utilized. The fluid developed by the burning of the fuels in the two cartridges passes through port 25 to tubular member 22.

The embodiment illustrated in FIGURE 4 is a rivet head type primer having bottom 32 inserted through an opening in the bottom of cup 34. This type of primer may be used instead of the type shown in FIGURE 2 and, indeed, this type is preferred in cartridges for some purposes. A dielectric washer 33 lies between the shoulder of button 32 and base of cup 34 preventing electrical contact therebetween. A metal washer 36, which may be brass, copper, or the like lies inside cup 34 and is separated from the base of cup 34 by a dielectric washer 35. Washer 36 is in electrical contact with annular flange 44 of button 32. A priming composition 41 substantially fills cup 38 lying in cup 34. Bridgewire 39 is soldered to post 45 of button 32 and to the flange of cup 38 that forms the partially closed base of that cup. A dielectric washer lies between the flange of cup 38, washer 36 and button 32 preventing electrical contact therebetween. This particular type of primer has been found especially advantageous because of the effective seal against gas leakage obtained with such primers, particularly when a layer of resinous sealer is placed between the pocket wall and primer. In order to further seal the primer and pocket assembly against gas leakage and against the entrance of moisture into the cartridge, the interstice between the pocket wall and the base of cup 34, that is, the opening around the button 32, is filled with a suitable resinous material such as epichlorohydron-bisphenol polymer or one of the other resins used for coating the Wall of the pocket 3 as described herein.

FIGURE 5 illustrates pocket 43 of the cartridge case With a coating 42 of resinous material on the sidewalls. The thickness of film 42 is grossly exaggerated for the purpose of illustration and ordinarily will not exceed about 0.005 to about 0.010 of an inch in thickness. The primer is inserted in the pocket after the coating has been applied to the sidewalls and a seal is obtained against any gas leakage between the primer and pocket 43 wall when the cartridge is fired. Film 42 is also advantageous in assembling the primer with the cartridge because it acts as a lubricant as the primer is inserted in the pocket.

Cartridge case 1 may be formed from any material which has properties such that it will rupture adjacent the ports in the sleeve when the cartridge is fired. An aluminum alloy or pure aluminum is preferred because it can be shaped into a cartridge case by cold working such as by extrusion or cold drawing and has the necessary physical properties to rupture when the cartridge is fired, but cartridge cases of magnesium, steel, brass, and other similar metals may be utilized. The metal, of course, must be sufficiently ductile to be bent over to form the crimp without fracturing. The head portion must be relatively thick as shown in the drawing to adequately support the primer, or a basewad must be used.

Wad 6 may be formed from paper or any suitable plastice material such as polyethylene, ethyl cellulose and the like and it is preferred but not necessarily essential that its flange be bound to the wall of the cartridge case with a suitable adhesive material. End wad 5 is formed from a suitable moisture resistant plastic such as nitrocellulose, polyvinyl chloride, ethyl cellulose or cellulose acetate or from a metal such as aluminum or magnesium. The wad should be made of such a material that it will be consumed upon ignition of the cartridge. The main fuel charge 7 may be a smokeless powder having a nitrocellulose base but is preferably a double base powder containing a major amount of nitrocellulose and a minor amount of nitroglyeerine. A powder particularly well suited as a fuel contains from about 20 to. about 25 percent nitroglycerine, from about 70 percent to about 75 percent nitrocellulose, about 5 percent stabilizer such as ethyl centralite, diphenylamine and the like, and about 2 percent of a suitable oxygen bearing salt such as barium nitrate, potassium nitrate, lead peroxide or a fifty-fifty mixture of barium nitrate and potassium nitrate or the like. This powder should have a length of about one-half inch, a diameter of about one-fourth inch and a web of about 0.05 inch. Any other powder having a burning rate substantially equivalent to the powder of this composition and physical measurements may be utilized. In this preferred powder, each grain has seven perforations extending longitudinally therethrough. These perforations have a diameter of about 0.015 inch.

The faster burning powder is preferably a globular smokeless powder of the type provided by Schaefer in US. Patent 2,160,626 and coated with nitroglycerine. However, other powders ignitable by the primer and capable of igniting the main fuel charge can be utilized for the purpose. In a preferred embodiment, the globular powder has a composition of about percent nitroglycerine, about 77 percent nitrocellulose, about 1 percent diphenylamine, about /2 percent deterrent and the bal ance graphite on the surface thereof. Grains passing through a screen having circular openings 0.028 inch and remaining on a similar screen having 0.018 inch openings and of the foregoing composition are preferred. The grains are preferably flattened by rolling or other means.

The primer cups may be made from any suitable metal but brass, because of its cold working properties and electrical conductivity, is preferred. Likewise, the contact buttons 27 and 32 may be formed from any suitable about 175 'microns. Zirconium of the two granulations is advantageous over zirconium of either granulation alone because the presence of some of the finer granulations improves ignition of the priming, but it cannot all be of the finer granulation because the resulting composition frequently ignites spontaneously when the mix becomes dry. Other priming compositions adapted to be ignited by a heated wire, such as a mixture of about 30 to parts normal lead styphnate, 20 to 40 parts oxidizing salt such as barium nitrate, lead peroxide, potassium nitrate and the like, about 0 to 6 parts tetracene, about 5 to 10 parts aluminum and about 10 to 20 parts anti mony sulfide may be utilized in some embodiments, if desired.

As indicated hereinbefore the end closure must be sealed against moisture at the pressure and temperatures found at high altitudes. This is achieved by placing a layer of sealer 31 between the end of the cartridge case and the external surface of the wad. Another layer of sealer may be placed between the base of wad and the annular ring 26 as shown at 30 in the drawing to further insure against moisture entering the cartridge. The end of the case is turned over and placed against the wad and thus tightly compresses the base of the wad against ring 26 causing the base to become embedded in the sealer 30. The composition used to seal the junctures between the wad 5 and cartridge case is preferably an epichlorhydron-bisphenol A polymer. Such a material is an adhesive as well as a moisture proofing material. An adhesive manufactured by the Shell Chemical Corporation is an example of a trade product having this composition, namely,

metal but preferably from brass or copper. The dielectric washers utilized in the primer may be rubber, synthetic rubber or any suitable plastic material such as vinyl chloride, vinyl acetate, a copolymer of vinyl acetate and vinyl chloride, polyamide, vinylidine, and the like. The resistance wire may be of any suitable material which will become heated by an electric current. For example, a nickel-chromium alloy, platinum, palladium, tungsten and platinum-tungsten alloys may be utilized to advantage.

In assembling the components of the primer shown in FIGURE 2, the button 27 is placed in cup-shaped cylinder 11 with a dielectric material between it and the case wall. A washer of dielectric has previously been placed over the button and about the protuberance which will be in electrical contact with the resistance wire. The flanged cylinder 29 is next inserted in cylinder 11 and resistance wire 17 is soldered to the flange and protuberance 16. Priming composition is then placed in the cylinder 29.

The primer must be such that it is adapted to be ignited by the heated resistance wire and will ignite the booster fuel charge. Any such composition is suitable but one containing zirconium, a primary explosive and a suitable oxygen bearing salt has been found particularly advantageous because it is particularly well suited for igniting the booster charge. The preferred composition contains from about 15 parts to about 100 parts normal lead styphnate or similar primary explosive such as basic lead styphnate, diazodinitrophenol, tetracene, or the like, from about 10 parts to about 40 parts zirconium having a granulation within the range from about microns to about 150 microns, about 3 parts to about 25 parts zirconium having a particle size of less than about 45 microns and from about 20 parts to parts lead peroxide, or other oxidizing salt, such as barium nitrate, potassium nitrate, sodium nitrate and the like having a particle size within the range from about 45 microns to and particularly a liquid type of this resin having a viscosity of the pure resin at 25 C. of about Z Z (Gardnerholdt), or about -160 poises, with an epoxide equivalent of -210. Any other suitable resin including nitrocellulose lacquer, cellulose acetate butyrate and silicone resins and the like may be utilized but the abovenoted resin has been found most resistant to water vapor. The resin is applied while dissolved in a suitable solvent such as ethyl acetate, acetone, methylethyl ketone or the like and air dried to produce the layer or fillet of sealer.

The fixture 18 can be made from steel or any other suitable metal.

Although the invention has been described in detail in the foregoing in connection with preferred embodiments, it is to be understood that such detail is solely for the purpose of illustration and that variations can be made in the embodiments by those skilled in the art without departing from the spirit of the invention except as limited by the appended claims.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. A primer adapted to be fired electrically comprising a metal cylinder having an open end and an opposite end partially closed by a flange integral with and perpendicular to the sidewalls of the cylinder, a button formed of an electrical conductor having a cylindrical protuberance extending into the opening bordered by said flange and on the opposite side thereof a second protuberance, a dielectric material between the button and the walls of said cylinder, a dielectric washer lying on said button and about the second said protuberance, a second smaller cylinder having an open end and a partially closed end having a flange integral with the side walls thereof and substantially perpendicular thereto, a resistance Wire secured to the flange and lying across the opening in said partially closed end, a priming composition adapted to be ignited by said resistance wire when 7 8 heated lying about the resistance wire, said resistance wire about 10 to about 40 parts zirconium having a granulabeing in electrical contact With said button. tion of from about 45 microns to about 150 microns and 2. The primer of claim 1 with its priming composition from about 3 parts to about parts zirconium having a comprising about 15 parts to about 100 parts normal lead granulation of less than about 45 microns.

stypnate, from about 10 parts to about parts zirconium 5 having a granulation of from about microns to about References Cited in the file of this patent 150 microns, about 3 parts to about 25 parts zirconium UNITED STATES PATENTS having a granulation less than about 45 microns and from 2 0 51 Seavey J 19, 1937 about 20 parts to about parts inorganic oxidizing salt. 2,473 501 Patterson A 9, 1949 3. The primer of claim 1 with its priming composition 2,649,736 Phillip Aug. 25, 1953 comprising from about 15 to about parts primary eX- 2,685,837 Sage Aug. 10, 1954 plosive, about 20 to about 50 parts oxidizing salt and from 2,696,429 Hart Dec. 7, 1954 

